The present invention relates to improvements to appliances intended for the ultra- or micro-filtration of liquids, especially water, by means of membranes consisting of fibers grouped in the form of tubular bundles, in which filtration takes place from the inside of the fiber towards the outside ("inner skin").
Such appliances take the form of a cylindrical containment, the ends of which are domed and in which the bundles of filter elements are either arranged between two superposed floors or fixed to a single floor.
These appliances are fed with liquid, such as water to be filtered, and the process requires a recirculation which is necessarily very great because of the design of the filter element, and which can reach ten times the production rate, in order to ensure an effective scavenging of the inside of the fibers forming the bundles.
Furthermore, at more or less frequent intervals, these fibers have to be cleared of particles, deposited on the surface during filtration, by being washed with water. This washing, called backwashing, is carried out by reversing the direction of the pressures in the appliance, and therefore by reversing the direction of flow through the wall of the fibers, thus causing these particles to be detached.
According to the conventional technique, the driving element or elements for the recirculation, such as pumping stations, turbines, screws or the like, are located outside the appliance.